>>5862095For art style I think it's best described as cartooning or children's illustration - I don't think there's a specific discrete name for this genre. As for how it's accomplished the first one looks like gouache over pencil to me (maybe some dry brush or some sort of pastel on the fir, although it might just be paper texture).
The others are watercolor paintings over pencils and inks.
One of the best resources for the technical process here is the "Famous Artists Course" (I believe it's floating around in the books thread or the sticky) - specifically the chapters on gouche (which they refer to as "opaque" in every instance, but it's gouache or a similar poster paint) and the chapter on ink wash - which is applicable to this kind of watercoloring. As far as I recall they focus heavily on monochrome (which is great, you should probably learn in that way first) but beyond that any good watercolor book would get you the rest of the way. As for the style itself, like most cartooning styles, you really need a firm grasp on the fundamentals and do a bunch of studies of this and similar artist until you can learn enough about how they stylize things.